Oil-free screw compressor is a common air compressor, which can compress air through the rotation of the screw, and does not need to use lubricating oil to lubricate and cool the screw.

Working principle

In the compressor body, a pair of spiral rotors meshing with each other are arranged in parallel. Usually, the rotor with convex teeth outside the pitch circle is called male rotor or male screw. The rotor with concave teeth in pitch circle is called negative rotor or negative screw. Generally, the positive rotor is connected with the prime mover, and the positive rotor drives the negative rotor to rotate the last pair of bearings on the rotor to realize axial positioning and bear the axial force in the compressor. Cylindrical roller bearings at both ends of the rotor enable the rotor to achieve radial positioning and bear the radial force in the compressor. At both ends of the compressor body, orifices with certain shapes and sizes are respectively opened. One is for inhalation, called air inlet; The other is for exhaust, called exhaust port.

Intake air

When the rotor rotates, the groove space of the yin-yang rotor is larger when it turns to the opening of the air inlet wall. At this time, the groove space of the rotor is communicated with the air inlet, because the gas in the groove is completely discharged when the exhaust is completed, the groove is in a vacuum state, when it turns to the air inlet, the outside gas is sucked and enters the groove of the yin-yang rotor along the axial direction. When the gas fills the whole groove, the end face of the inlet side of the rotor turns away from the inlet of the casing, and the gas in the groove is closed.

Compression

Screw air compressor working process detailed analysis of the compression process: Yin and Yang rotor in the end of the suction, the Yin and Yang rotor teeth will be closed with the casing, at this time the gas in the groove no longer outflow. Its meshing surface gradually moves to the exhaust end. The tooth groove space between the meshing surface and the exhaust port gradually becomes smaller, and the gas in the tooth groove is compressed and the pressure is increased.

Exhaust

Exhaust process: When the rotor meshing face turns to communicate with the casing exhaust port, the compressed gas begins to exhaust until the meshing face between the tooth tip and the groove moves to the exhaust end face. At this time, the groove space between the meshing face of the yin and yang rotors and the casing exhaust port is 0, that is, the exhaust process is completed. At the same time, the groove length between the rotor meshing face and the casing intake port reaches the longest, and the intake process is carried out again.

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Advantages of oil-free screw air compressor:

1. Oil-free screw air compressor does not need to use lubricating oil, so it can greatly reduce maintenance costs and reduce oil pollutants in the air.

2. Because oil-free screw air compressor does not need to use lubricating oil, it can also avoid faults caused by oil corruption or excessive use.

3. The oil-free screw air compressor has low noise and small vibration when working, so it is suitable for occasions where quiet environment is needed.

4. Because there is no lubricating oil in the oil-free screw air compressor, the problem of environmental pollution caused by oil leakage is avoided.

Disadvantages of oil-free screw air compressor:

1. Because there is no lubricating oil to cool the screw in the oil-free screw air compressor, it is easy to deform or burn the screw in high temperature environment.

2. The cost of oil-free screw air compressor is usually high, so it is not suitable for all occasions.

3. The compression ratio of oil-free screw air compressor is usually low, so it may not meet the requirements in some applications requiring high-pressure gas.